When Stephanie Goldner went to Costco Canada’s website, she saw a page that popped up before she started shopping.

She could get a free gift, paying just $5.95 for shipping, by filling out a short survey.

“I never do this kind of thing, but because it was Costco, I thought it was okay,” she said about the offer.

Her gift, a set of three face creams, showed up quickly. She forgot about it until a few weeks later, when she found a $179.95 charge on her credit card statement.

The face-cream company told her that she hadn’t returned the “trial items” within 14 days and was charged the full cost.

Costco Canada has posted a message about pop-up ads on its site, warning people not to provide personal information in order to receive a gift. The survey was not associated with or sponsored by Costco, spokesman Ron Damiani told me.

I’ve written before about the free-sample scam. Many smart people, enticed by the lure of a test run, give their credit card numbers to cover a small shipping charge and end up roped into a high-priced monthly subscription.

They can usually stop the shipments by notifying their credit card issuers. But they may be denied a refund because they didn’t read the fine print.

Until Goldner wrote me, I didn’t realize the free-sample ads had moved beyond Facebook to take up residence on large retailers’ websites.

A Google search led to other laments about the pop-up ads at Costco.ca. The Canadian Anti-Fraud Centre has received complaints, too.

“This was no separate window. This was before you could get into the Costco site,” said one commenter.

“On the original pop-up, there was no mention of a trial period, no mention of an automatic refill program and no mention of the $348 charge I would be billed,” said another commenter (also anonymous).

March is Fraud Prevention Month in Canada, designed to raise awareness of the different traps that can ensnare you as a consumer.

But in my view, scammers are always a few steps ahead of you. Once you spot their tricks, they’ve already headed down another path you didn’t anticipate.

Fraud artists are experts in appealing to your emotions. The free-sample scam, for example plays on your greed. The Canada Revenue Agency extortion scam plays on your fear. The emergency scam, where you are asked to bail out a friend or family member in dire need, plays on your sense of generosity.

I almost fell for an email scam that seemed believable.

I received a receipt from the Apple iTunes store showing I had bought four items worth about $70. Knowing this was a mistake, I felt a huge sense of relief to see a line at the bottom: “If you did not authorize this purchase, click here for a refund.”

I’d already clicked the link before coming to my senses. Ironically, I was almost defrauded while trying to report a fraud.

A new book by psychologist Maria Konnikova, The Confidence Game: Why We Fall for It … Every Time, talks about our vulnerability to con artists’ emotional appeals.

Everyone has heard the saying, “if it seems too good to be true, it probably is.” Or its close relative, “there’s no such thing as a free lunch.” But when it comes to ourselves, we tend to latch onto that “probably.” As in, if it seems too good to be true — it is, unless it’s happening to me. I deserve good returns on my money, at long last.

“When we see other people talking about their unbelievable deal or crazy good fortune, we realize at once that they’ve been taken for a sucker. But when it happens to us, well, I am just lucky and deserving of a good turn,” Konnikova writes.

Fraudsters may catch us when we feel sad, lonely or stressed. The more we have on our minds, the less attentive we are to details.

Victoria Beed, for example, received a call at 5:30 a.m. from a toll-free number. The caller, who knew her name, was looking at possibly fraudulent credit card activity and mentioned a 4 a.m. purchase on eBay.

“Because the call had woken me up, I was less sure of myself at first,” she said. “But after a few minutes, I told them the call sounded odd. Suddenly, they hung up.”

Ellen’s advice

As humans, we feel first and think later. That’s why we fall for confidence games.

The key to fraud prevention is to avoid acting impulsively. Build in time to reflect and research before clicking a link or giving personal information to a persuasive but pushy criminal.